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Explainer: What Is Common Variable Immunodeficiency (CVID)?

Common variable immunodeficiency (CVID) is a primary immune deficiency – one of more than 450 types. Patients are vulnerable to serious infections and health complications, but treatment can reduce those risks.

illustration of Y-shaped antibodies

Common variable immunodeficiency (CVID) is a primary immune deficiency, a group of 450+ rare, chronic conditions. The immune system is vast and complex, but what primary immune deficiencies have in common is that the patient’s immune system is not functioning as it should.

For someone diagnosed with CVID, a doctor has determined that the person’s body does not adequately produce antibodies, which are a key weapon in the fight against infections. The severity of CVID and other PI varies among patients.

Video: Meet a new mom who has CVID and is raising twin boys

How common is CVID?

CVID is among the most commonly diagnosed types of primary immune deficiencies, according to the Immune Deficiency Foundation. It has “common” in its name but it’s still a rare disease, which in the United States means that fewer than 200,000 patients are affected, says the National Organization for Rare Disorders (NORD).

This is because primary immunodeficiencies are uncommon overall. NORD explains that CVID is among the most prevalent primary immune conditions that have symptoms. It affects every one in 25,000 to 50,000 people, reports Mayo Clinic.

Diagnosis of CVID varies worldwide, according to German researchers Weifenbach, Schneckenburger, and Lötters. They found that CVID affects between 0.001 and 3.374 per 100,000 people. Countries where the standard of living is higher report higher numbers of CVID patients than in places that score lower on the Human Development Index, a measure created by the United Nations to gauge longevity, quality of life and level of education among populations.

What causes CVID?

For most people with CVID, the exact causes remain unclear. NORD notes that genetic differences can explain around 20% of CVID cases. CVID likely has both genetic and environmental causes, according to the National Library of Medicine (NLM).

Genetic differences can affect immune cells and the production of immunoglobulins, explains the National Institute of Allergy and Infectious Diseases. People with CVID often have lower levels of IgA and/or IgM, as well as T cell defects that also may contribute to autoimmune problems, the IDF says.

What are the symptoms of CVID?

Frequent infections are a common symptom of primary immune deficiencies, including CVID.  For someone with CVID, the lack of antibodies reduces the person’s ability to ward off viruses and bacteria. Getting sick a lot takes a physical and emotional toll. Bacterial and viral infections often affect the respiratory system. Recurrent, severe lung infections can cause lasting damage to the lungs, according to the IDF.

About 20% of people with CVID have signs of immunodeficiency in childhood and are diagnosed when they’re young. Others may go decades before they are diagnosed.

An autoimmune condition can be another sign of CVID. About 25% of people with CVID have autoimmune disorders, such as rheumatoid arthritis, that attack the body’s own organs and tissues, says the National Library of Medicine. With rheumatoid arthritis, a person experiences joint pain and stiffness. Some autoimmune conditions can lower platelet counts and destroy red blood cells.

Gastrointestinal problems are also common, impacting around 21% of people with CVID, according to the Immune Deficiency Foundation. Other problems can develop in the liver and lymph nodes, including lymphoid cancer.

How is CVID diagnosed?

Lab results that confirm low levels of serum immunoglobulins help diagnosing CVID. Decreased antibody levels after exposure to vaccine antigens may be a sign of CVID. Tests assessing lymphocyte levels and B-cell markers can also give an immunologist additional information for making a diagnosis.

Diagnosing CVID can be challenging due to the lack of knowledge and clear diagnostic criteria, note Ghafoor and Joseph, medical researchers from Nova Southeastern University School. Symptoms of CVID vary greatly among individuals and can mimic those of other immune diseases. Physicians may need to rule out other conditions before confirming a diagnosis of CVID, according to Ghafoor and Joseph.

Immunoglobulin replacement therapy treats symptoms of CVID and these infused medicines help support the immune system and prevent infections. The medicines may be delivered intravenously (IV) or subcutaneously (SC). IV treatment is administered through a vein with a needle or catheter. With IVIg, most patients must receive treatment at their doctor’s office or an infusion clinic.

Subcutaneous infusions, on the other hand, are injected into fatty tissue just underneath the skin. Once trained, SCIg infusions allow patients to self-administer the treatment at a recommended infusion site location of their choice, providing greater convenience and flexibility in managing their disease.

Patients who get frequent infections also might receive broad-spectrum antibiotics for chronic infections, according to the Immune Deficiency Foundation. In that way, a PI patient is like anyone else. Antibiotics are prescribed for infections, but someone who has CVID might not respond as well and it may take longer for them to recover.

Regular medical care is important for people with CVID. The Immune Deficiency Foundation recommends that doctors monitor patients with CVID for autoimmunity, GI symptoms, and changes in lung function.

What is the outlook for people with CVID?

Having CVID can increase the risk of other health problems, but according to The Cleveland Clinic, patients can lead full lives if they get regular, appropriate treatment and make lifestyle adjustments. Jodi Taub has CVID and works as a clinical psychotherapist while also sharing advice on about managing a chronic condition. Writer Emily Gordon successfully co-created the film "The Big Sick" despite the daily challenges of living with CVID. She emphasizes the importance of acceptance and self-advocacy.

"You control very little in this life," says Gordon. "And I think the sooner you can just kind of sit with that and then figure out what you can control… the better."

Learn more about immune deficiencies.